A gaming term for an under-mounted grenade launcher such as the M203 or any other kind of launched explosive (RPG, Thumper, etc) used in first person shooter games such as Call of Duty: Modern Warfare 2 or Battlefield: Bad Company 2. Use of such a weapon to get kills is considered 'cheap', since it requires very little skill to use. 'Noob' is a term for a newcomer to a game, and is used as an insult in gaming communities.

Damn, that noob got me with his noob tube for the eighth time this round!

Reference to a grenade launcher type weapon featured in several warfare silmulation games, both online and offline.
Takes very little skill to use and can kill whole groups of enemies with a single indirect hit, yet the explosion needs to be fairly close.

To be used liberally against elitist gamers who play games all day because they can't get jobs and whenever they can't win they start crying. Much amusement to be had reading their abuse.